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Residue Leu940 has a crucial role in the linkage and reaction specificity of the glucansucrase GTF180 of the probiotic bacterium Lactobacillus reuteri 180.

ABSTRACT: Highly conserved glycoside hydrolase family 70 glucansucrases are able to catalyze the synthesis of ?-glucans with different structure from sucrose. The structural determinants of glucansucrase specificity have remained unclear. Residue Leu(940) in domain B of GTF180, the glucansucrase of the probiotic bacterium Lactobacillus reuteri 180, was shown to vary in different glucansucrases and is close to the +1 glucosyl unit in the crystal structure of GTF180-?N in complex with maltose. Herein, we show that mutations in Leu(940) of wild-type GTF180-?N all caused an increased percentage of (?1?6) linkages and a decreased percentage of (?1?3) linkages in the products. ?-Glucans with potential different physicochemical properties (containing 67-100% of (?1?6) linkages) were produced by GTF180 and its Leu(940) mutants. Mutant L940W was unable to form (?1?3) linkages and synthesized a smaller and linear glucan polysaccharide with only (?1?6) linkages. Docking studies revealed that the introduction of the large aromatic amino acid residue tryptophan at position 940 partially blocked the binding groove, preventing the isomalto-oligosaccharide acceptor to bind in an favorable orientation for the formation of (?1?3) linkages. Our data showed that the reaction specificity of GTF180 mutant was shifted either to increased polysaccharide synthesis (L940A, L940S, L940E, and L940F) or increased oligosaccharide synthesis (L940W). The L940W mutant is capable of producing a large amount of isomalto-oligosaccharides using released glucose from sucrose as acceptors. Thus, residue Leu(940) in domain B is crucial for linkage and reaction specificity of GTF180. This study provides clear and novel insights into the structure-function relationships of glucansucrase enzymes.

SUBMITTER: Meng X

PROVIDER: S-EPMC4239627 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature

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Residue Leu940 has a crucial role in the linkage and reaction specificity of the glucansucrase GTF180 of the probiotic bacterium Lactobacillus reuteri 180.

Meng Xiangfeng X Dobruchowska Justyna M JM Pijning Tjaard T López Cesar A CA Kamerling Johannis P JP Dijkhuizen Lubbert L

The Journal of biological chemistry 20141006 47

Highly conserved glycoside hydrolase family 70 glucansucrases are able to catalyze the synthesis of α-glucans with different structure from sucrose. The structural determinants of glucansucrase specificity have remained unclear. Residue Leu(940) in domain B of GTF180, the glucansucrase of the probiotic bacterium Lactobacillus reuteri 180, was shown to vary in different glucansucrases and is close to the +1 glucosyl unit in the crystal structure of GTF180-ΔN in complex with maltose. Herein, we sh ...[more]

PMID: 25288798

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Project description:Probiotics and commensal intestinal microbes suppress mammalian cytokine production and intestinal inflammation in various experimental model systems. Limited information exists regarding potential mechanisms of probiotic-mediated immunomodulation in vivo. In this report, we demonstrate that specific probiotic strains of Lactobacillus reuteri suppress intestinal inflammation in a trinitrobenzene sulfonic acid (TNBS)-induced mouse colitis model. Only strains that possess the hdc gene cluster, including the histidine decarboxylase and histidine-histamine antiporter genes, can suppress colitis and mucosal cytokine (interleukin-6 [IL-6] and IL-1? in the colon) gene expression. Suppression of acute colitis in mice was documented by diminished weight loss, colonic injury, serum amyloid A (SAA) protein concentrations, and reduced uptake of [(18)F]fluorodeoxyglucose ([(18)F]FDG) in the colon by positron emission tomography (PET). The ability of probiotic L. reuteri to suppress colitis depends on the presence of a bacterial histidine decarboxylase gene(s) in the intestinal microbiome, consumption of a histidine-containing diet, and signaling via the histamine H2 receptor (H2R). Collectively, luminal conversion of l-histidine to histamine by hdc(+) L. reuteri activates H2R, and H2R signaling results in suppression of acute inflammation within the mouse colon.Probiotics are microorganisms that when administered in adequate amounts confer beneficial effects on the host. Supplementation with probiotic strains was shown to suppress intestinal inflammation in patients with inflammatory bowel disease and in rodent colitis models. However, the mechanisms of probiosis are not clear. Our current studies suggest that supplementation with hdc(+) L. reuteri, which can convert l-histidine to histamine in the gut, resulted in suppression of colonic inflammation. These findings link luminal conversion of dietary components (amino acid metabolism) by gut microbes and probiotic-mediated suppression of colonic inflammation. The effective combination of diet, gut bacteria, and host receptor-mediated signaling may result in opportunities for therapeutic microbiology and provide clues for discovery and development of next-generation probiotics.

Dataset Information

Residue Leu940 has a crucial role in the linkage and reaction specificity of the glucansucrase GTF180 of the probiotic bacterium Lactobacillus reuteri 180.

Publications

Residue Leu940 has a crucial role in the linkage and reaction specificity of the glucansucrase GTF180 of the probiotic bacterium Lactobacillus reuteri 180.

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